1. Field of the Invention
The present invention relates to a valve timing control apparatus for an internal combustion engine having a variable valve timing mechanism which varies an opening-and-closing timing (a valve timing) of an intake valve and/or an exhaust valve of an engine.
2. Description of the Related Art
As a valve timing control apparatus for an internal combustion engine, there is an apparatus disclosed in Japanese unexamined patent publication No. 11-241608. In this apparatus, the variable valve timing mechanism is controlled such that a valve timing of an intake valve is set to a maximum retard timing which is retarded at the maximum by inertial rotation immediately after stopping the engine, and on the other hand, the valve timing of the intake valve is set to a starting time timing at a further advance side than the maximum retard timing at the time of starting the engine.
The above-described variable valve timing mechanism in a conventional art is a so-called hydraulic mechanism, and because it is a structure in which a valve timing is varied by supplying an oil pressure due to a crankshaft being started to rotate by starting cranking at the time of starting the engine, a speed of varying the opening-and-closing timing depends on a discharge pressure of an oil pump.
Therefore, a delay in the time from the maximum retard timing to the starting time timing is brought about at the time of starting the engine in which the discharge pressure of the oil pump is low, and there is the possibility that fuel injection/ignition is carried out before reaching the starting time timing, and there is the concern that deterioration in emission and combustive instability are brought about.
Here, a delay as described above can be improved by using an electromagnetic mechanism as the variable valve timing mechanism. However, in order to avoid deterioration in emission and combustive instability at the time of starting, it has been required to be able to more accurately carry out starting in the starting time timing, such as that the valve timing of the engine valve is more rapidly controlled to be the starting time timing at the time of starting the engine, or the like.